Method of enameling wire



Juiy 5 E9358 (1. s. FULLER METHOD OF ENAMELING WIRE Filed March 27, 1936 INVENTOR C. .S. FULLER A T TO/PNEV Patented July 5, 1938 UNITED STATES.

PATENT OFFICE Telephone laboratories,

Incorporated, New

York, N. Y., a corporation New York Application March 27, 1936, Serial No. 71,149

Glaims. (O1. 91- -70) This invention relates to electrical conductors and more particularly to a method of coating conductors with insulation such as enamel insulation.

In the process of coating electrical conductors with insulation, and, especially in the case of coating wires with an enamel or the like, it is the practice in some instances to pass the wire through a bath of suitable coating material one or more times with a drying or baking operation after each coating. However, it has been discovered that oftentimes the resulting insulating coating contains numerous weak points and imperfections which are due to the initial condition of the wire being coated instead of improper methods of applying the insulation. 'An examination of such wire discloses considerable variability in its surface, there being ridges, slivers and other such flaws present. These irregular projections make it extremely difiicult to coat with an even thickness of insulation. The result.- ing insulated wire on account of these imperfections often has weak points at which the slivers etc., almost project through the insulation, or

uninsulated points at which the slivers actually extend through the coating. While for some uses such defects in insulation may be negligible, in others such as in the manufacture of relay coils, cables and the like wherein turns of wire are tightly positioned together, these defects materially reduce the efficiency and life of the apparatus.

An object, therefore, of the present invention is an insulated wire having substantially no defects in the insulated coating.

Another object of the invention is a method of improving the surface condition of the wire 'prior to coating with a final insulating layer.

A further object of the invention is a combined process of continuously improving the surface condition of the wire and coating the wire.

Still another object of the invention is a process of removing defects in the surface of the wire after it has been coated with one or more layers of insulation.

In accordance with the present invention, these and other objects are attained by coating a wire by any suitable process with an insulating coating such as an enamel coating and then passing the coated wire through a current carrying liquid such .as mercury or an electrolyte. A potential is applied between the wire and the liquid electrode. As each defect in the insulation passes through the liquid electrode the projecting slivers and the like are subjected to a sufllcient current to cause arcing. The heating effect of the current and the chemical effect 0! the arc destroy the particle or defect causing the low resistance. The wire is then recoated in any suitable manner and, if necessary, redrawn through the liquid electrode. The final coating will cover up any cratersformed by the electric current and will result in an improved and evenly coated wire. 1

This invention will be more clearly understood from the accompanying detailed description and the drawing which shows in schematic form apparatus for producing improved insulated wire.

As shown in the drawing, thewire I to be coated is wound upon spool 2 which is positioned on shaft 3. The wire 5 passes over guide pulley 4 around driving drum 5 to the tank 8 containing the insulating material H where it passes around guide rollers I and 8, and 9 and Ill, and receives a coating of the insulating compound. The coated wire I then passes through a suitable drying or baking oven l2. Preferably the enameled wire is baked in the oven l2 until dry. In many cases the wire will be coated imperfectly and slivers and other projections will extend through the coating. On emerging from the baking oven l2, the coated wire passes around driving drum l3 and through the current carrying liquid N which is held in a suitable receptacle I5. While this receptacle may be of any suitable construction, it has been found satisfactory to form the bottom I 6 of metal and the sides I! of soft rubber. The current carrying liquid may be an electrolyte or mercury. The wire enters and leaves this receptacle 15 through slits l8 and IS in the rubber walls and does not come in contact with the metal base IS. The elastic rubber walls grip the wire tightly and prevent any of the current carrying liquid N from leaving the container through the slits.

A potential is applied to the coated wire and to the conducting fluid and when a projection on the wire extends through the insulation and contacts with the conducting liquid current flows through this projection and over the wire. As shown in the drawing, a potential is applied to the conducting liquid from generator 20 through the windings 2i and 22 of the transformer over conductor 23 to the base IS which is in contact with liquid N. One side of the transformer winding 22 is grounded at 21. The wire I is grounded at 25 through drum '5, shaft 28 and contact 24. This permits a current to flow from. transformer 28 through the conducting liquid ll over the slivers which project through the initial insulating coating and over the wire to ground 2|. Since the slivers are small, they will be destroyed by the heating eilect of the current and also by the arcing formed at that point. The wire will now have a very small crater in the coating in place of the sliver and this is illled up by a subsequent coating of enamel. The wireis carried around drum 5 a second time and again passes through the tank containing the insulating material where it receives a second coating and through baking oven 12, around drum II and to the current carrying liquid ll where any remainingslivers or other such defects are removed electrically. The wire again passes around drum I and is given a final coating ofinsulation and the coating is baked on in oven II. On leaving oven II, the wire is conducted over drum I! to guide pulley 28 and is wound upon spool 43 which is turned by shaft 26. It is, of course, obvious that the apparatus may be enlarged so that the wire may be passed through the liquid electrodes and coating bath as many times as is desirable, and that it can be constructed so that more than one wire can be enameled at a time.

As shown in the drawing, the drums l and II are driven at the same rate by motor 30 through gears ii and 32, shaft 3!, gears I4 and 35, shaft 36, gears 31 and 38 and shaft 28; and gears 39 and-l0 and shaft I. The take-up spool 43 is also driven by motor 30 through the train of gearing mentioned above and shaft 36 which carries friction clutch 42. when shaft 41 is turned, it turns gears 45 and 46 which rotate spool 43 through shaft 28., As an increased number of turns of wire is takenup on spool l3 slippage of friction clutch 42 will increase thereby compensating for the increase in eifective diameter of the spool 43 and preventing undue ten- 1 sion on the coated wire.

What is claimed is:

wire with insulation, passing the coated wire and electrode sufficient to reduce any projec- I tions of the wire through the coating, and subsequently coating and baking the coated wire a second time.

. 3. The method of improving the continuity of wire with insulation, baking said coating in an oven, subjecting the coated wire while it is passing through mercury to a suillcient potential to remove substantially any projections of the wire through the insulation, and filling in any voids in the insulating coating by recoating the wire.

4. The method of improving the continuity of insulation on wire which comprises coating the wire with enamel, baking said coating in an oven until dry, subjecting the enameled wire while it is passing through mercury to asuflicient potential to remove substantially any portions of the wire extending through the insulation, and filling in any voids in the enamel coating by recoating the wire.

5. The method of manufacturing insulated wire comprising coating the wire with insulation, immersing the coated wire in a bath of mercury, impressing a suilicient potential across the wire and the bath to reduce substantially metallic projections of the wire protruding through said coating, applying a second coating of insulation to the wire, immersing the wire with the second coating of insulation thereon in a bath of mercury, impressing a sufficient potential across the wire and the bath to reduce metallic projections protruding through the coating and applying a third coating of insulation to the wire.

CALVIN S. FULLER.

insulation on wire which comprises coating the j 

